Design and realisation of tissue-equivalent dielectric simulators for dosimetric studies on microwave antennas for interstitial ablation

Thermal ablation therapies, based on electromagnetic field sources (interstitial or intracavitary antennas) at radio and microwave frequencies, are increasingly used in medicine due to their proven efficacy in the treatment of many diseases (tumours, stenosis, etc). Such techniques need standardized procedures, still not completely consolidated, as to analyze the behaviour of antennas for treatment optimisation. Several tissue-equivalent dielectric simulators (also named phantoms) have been developed to represent human head tissues, and extensively used in the analysis of human exposure to the electromagnetic emissions from hand-held devices; yet, very few studies have considered other tissues, as those met in ablation therapies. The objective of this study was to develop phantoms of liver and kidney tissue to experimentally characterise interstitial microwave antennas in reference conditions. Phantom properties depend on the simulated target tissue (liver or kidney) and the considered frequency (2.45 GHz in this work), addressing the need for a transparent liquid to easily control the positioning of the probe with respect to the antenna under test. An experimental set-up was also developed and used to characterise microwave ablation antenna performances. Finally, a comparison between measurements and numerical simulations was performed for the cross-validation of the experimental set-up and the numerical model. The obtained results highlight the fundamental role played by dielectric simulators in the development of microwave ablation devices, representing the first step towards the definition of a procedure for the ablation treatment planning.     

Morphology, origin and functions of the thrombocytes of Elasmobranchs

Thrombocytes of Torpedo marmorata Risso and Scyliorhynus stellaris L. (Elasmobranchs) are multiform from rounded to spindle-shaped. They originate in the spleen from prothrombocytes. They appear to be functionally correspondent to mammalian platelets because they form aggregates and adhere to glass and contain the same surface-connected canalicular system (SCCS) as in platelets, as proved by tannic acid treatment. Immunocytochemical staining have demonstrated, moreover, the presence in their cytoplasm of three platelet factors: platelet factor 4, beta-thromboglobulin and factor VIII related antigen. Stimulating agent, like collagen, ADP, noradrenaline, 5-hydroxytriptamine and thrombin induce aggregation of thrombocytes and the empting of their granules and vesicles containing very likely the platelet factors. The above observations leave few doubts on the functional equivalence of elasmobranch thrombocytes to mammalian platelets.     

Structure of the oxalate-ATP complex with pyruvate kinase: ATP as a bridging ligand for the two divalent cations

The 2 equiv of divalent cation that are required cofactors for pyruvate kinase reside in sites of different affinities for different species of cation [Baek, Y. H., & Nowak, T. (1982) Arch. Biochem. Biophys. 217, 491-497]. The intrinsic selectivity of the protein-based site for Mn(II) and of the nucleotide-based site for Mg(II) has been exploited in electron paramagnetic resonance (EPR) investigations of ligands for Mn(II) at the protein-based site. Oxalate, a structural analogue of the enolate of pyruvate, has been used as a surrogate for the reactive form of pyruvate in complexes with enzyme, Mn(II), Mg(II), and ATP. Addition of Mg(II) to solutions of enzyme, Mn(II), ATP, and oxalate sharpens the EPR signals for the enzyme-bound Mn(II). Superhyperfine coupling between the unpaired electron spin of Mn(II) and the nuclear spin of 17O, specifically incorporated into oxalate, shows that oxalate is bound at the active site as a bidentate chelate with Mn(II). Coordination of the gamma-phosphate of ATP to this same Mn(II) center is revealed by observation of superhyperfine coupling form 17O regiospecifically incorporated into the gamma-phosphate group of ATP. By contrast, 17O in the alpha-phosphate or in the beta-phosphate groups of ATP does not influence the spectrum. Experiments in 17O-enriched water show that there is also a single water ligand bound to the Mn(II). These data indicate that ATP bridges Mn(II) and Mg(II) at the active site. A close spacing of the two divalent cations is also evident from the occurrence of magnetic interactions for complexes in which 2 equiv of Mn(II) are present at the active site.(ABSTRACT TRUNCATED AT 250 WORDS)     

Locomotory behavior, contact inhibition, and pattern formation of 3T3 and polyoma virus-transformed 3T3 cells in culture

The social behavior of 3T3 cells and their polynoma virus-transformed derivative (Py3T3 cells) was examined by time-lapse cinemicrography in order to determine what factors are responsible for the marked differences in the patterns formed by the two cell lines in culture. Contrary to expectations, both cell types have been found to exhibit contact inhibition of cell locomotion. Therefore, the tendency of 3T3 cells to form monolayers and of Py3T3 cells to form crisscrossed multilayers cannot be explained on the basis of the presence versus the absence of contact inhibition. Morevover, with the exception of cell division control, the social behavior of the two cell types is qualitively similar. Both exhibit cell underlapping and, after contact between lamelliopodia, both show inhibition of locomotory activity and adhesion formation. Neither cell type was observed to migrate over the surface of another cell. The two cell types do show quantitative differences in the frequency of underlapping, the frequency with which contact results in inhibition of locomotion, and the proportion of the cell margin that adheres to the substratum. The increased frequency pf Py3T3 underlapping is correlated with the reduced frequency of substratum adhesions, which in turn favors underlapping. On the basis of these observations, it is concluded that the differences in culture patterns are the result of differences in the shapes of the individual cells, such that underlapping, and hence crisscrossing, is favored in Py3T3 cell interactions and discouraged in 3T3 cells.     

Acetyldehydrorishitinol,a rishitinol-related potato stress metabolite

A controlled atmosphere of ethylene in oxygen elevates rishitin and phytuberin levels in hypersensitive potato tuber tissue and the levels of hitherto unidentified stress metabolises. One of these was isolated and mass spectral, NMR, IR and UV data suggest the structure, 5,8-dimethyl-2[2 acetoxyisopropyl]-1,4-dihydronaphthalene. This new stress metabolise is related to rishitinol by loss of water and acetylation.     

Early life exposure to 2.45GHz WiFi-like signals: effects on development and maturation of the immune system

The development of the immune system begins during embryogenesis, continues throughout fetal life, and completes its maturation during infancy. Exposure to immune-toxic compounds at levels producing limited/transient effects in adults, results in long-lasting or permanent immune deficits when it occurs during perinatal life. Potentially harmful radiofrequency (RF) exposure has been investigated mainly in adult animals or with cells from adult subjects, with most of the studies showing no effects. Is the developing immune system more susceptible to the effects of RF exposure? To address this question, newborn mice were exposed to WiFi signals at constant specific absorption rates (SAR) of 0.08 or 4 W/kg, 2 h/day, 5 days/week, for 5 consecutive weeks, starting the day after birth. The experiments were performed with a blind procedure using sham-exposed groups as controls. No differences in body weight and development among the groups were found in mice of both sexes. For the immunological analyses, results on female and male newborn mice exposed during early post-natal life did not show any effects on all the investigated parameters with one exception: a reduced IFN-γ production in spleen cells from microwaves (MW)-exposed (SAR 4 W/kg) male (not in female) mice compared with sham-exposed mice. Altogether our findings do not support the hypothesis that early post-natal life exposure to WiFi signals induces detrimental effects on the developing immune system.     

NSP-interacting GTPase: A cytosolic protein as cofactor for nuclear shuttle proteins

Despite the significant progress in the identification of essential components of the nuclear transport machinery, some events of this process are still unclear. Particularly, functional information about the release of nuclear-exported macromolecules at the cytoplasmic side of the nuclear pore complex and their subsequent trans-cytoplasmic movement is lacking. Recently, we identified a cytoplasmic GTPase, designated NIG (NSP-interacting GTPase), which may play a relevant role in these processes. NIG interacts in vivo with the geminivirus NSP and promotes the translocation of the viral protein from the nucleus to the cytoplasm where it is redirected to the cell surface to interact with the viral movement protein, MP. Here we position the NIG function into the mechanistic model for the intracellular trafficking of viral DNA and discuss the putative role of NIG in general cellular nucleocytoplasmic transport of nucleic acid-protein complexes.Key words: geminivirus, NIG, NSP, nucleocytoplasmic trafficking, transport activity     

Genomic organization of the structural genes controlling the astaxanthin biosynthesis pathway of Xanthophyllomyces dendrorhous

The cloning and nucleotide sequence of the genes (idi, crtE, crtYB, crtl and crtS) controlling the astaxanthin biosynthesis pathway of the wild-type ATCC 24230 strain of Xanthophyllomyces dendrorhous in their genomic and cDNA version were obtained. The idi, crtE, crtYB, crtl and crtS genes were cloned, as fragments of 10.9, 11.5, 15.8, 5.9 and 4 kb respectively. The nucleotide sequence data analysis indicates that the idi, crtE, crtYB, crtl and crtS genes have 4, 8,4, 11, and 17 introns and 5, 9, 5, 12 and 18 exons respectively. In addition, a highly efficient site-directed mutagenesis system was developed by transformation by integration, followed by mitotic recombination (the double recombinant method). Heterozygote idi (idi+/idi-::hph), crtE (crtE+/crtE-::hph), crtYB (crtYB+/crtYB-::hph), crtI (crtI+/crtI-::hph) and crtS (crtS+/crtS-::hph) and homozygote mutants crtYB (crtYB-::hph/crtYB-::hph), crtI (crtI-::hph/crtI-::hph) and crtS (crtS-::hph/crtS-::hph) were constructed. All the heterozygote mutants have a pale phenotype and produce less carotenoids than the wild-type strain. The genetic analysis of the crtYB, crtl and crtS loci in the wild-type, heterozygote, and homozygote give evidence of the diploid constitution of ATCC 24230 strains. In addition, the cloning of a truncated form of the crtYB that lacks 153 amino acids of the N-terminal region derived from alternatively spliced mRNA was obtained. Their heterologous expression in Escherichia coli carrying the carotenogenic cluster of Erwinia uredovora result in trans-complementation and give evidence of its functionality in this bacterium, maintaining its phytoene synthase activity but not the lycopene cyclase activity.